Confidence in specific ID of recording

Levels of certainty

1) 100% certain

This means that the recordist and/or site coordinator believes that the identity of the species producing the sound is established beyond reasonable doubt. This level of certainty will ideally be based on direct observation and photographic documentation of an unequivocally identified bird or group of birds making the target sound. However, in many cases this is not possible or practical, and many vocalizations of birds not seen vocalizing, or poorly seen or unseen birds can nevertheless be identified with 100% certainty.
However, we recognize that there are a number of (fortunately rare) situations in which even what is deemed a “100%” certainty level species identification could be found to be incorrect:

  • Field identification mistakes
  • Reference material used for comparison or playback could be wrongly identified
  • Taxonomic changes
  • Mixups in narration or file naming
  • An unexpected, cryptically similar species could be present
  • Tape playback can attract the wrong bird, e.g.:
    • a different species vocalizing unnoticed in the background
    • an interspecific aggressive response
    • mixed flocking species
  • Mimicry
  • Similar-sounding species
  • Hybrids or aberrant individuals
  • A bird that is seen, even if apparently vocalizing, may not actually be that making the foreground sound
  • Tape playback or human imitation can be mistaken for a newly produced bird sound
  • Lack of documentation to indicate which sounds made by which species
  • Other forms of human error or avian vocal perversity

2) Slightly less than 100%

This means that the recordist and/or site coordinator is nearly but not totally certain, on evidence consulted, of the specific identification of the recording. This will normally be accompanied by explanatory notes, and given further comparative material, expert consultation, and/or further field experience it may be possible to move a given recording in this category to the 100% category. Rarely it may be shown to be incorrectly identified.

3) Less than 100%

This is a somewhat lower level of certainty than “slightly less than 100%”, but it was nevertheless deemed potentially useful to present the recording. Few recordings at this level are presented. Occasionally, it may be desirable to present recordings whose identification is known only to genus level or that definitely represent either of two or a few species. In such cases this will be clearly stated.

Some recordists have provided numerical estimates of their levels of certainty, and some have not provided estimates. When feasible, the site coordinator independently evaluates the identity of the recordings provided by others before uploading, as an additional check, and discusses potential discrepancies with the recordist.

“Basis for Specific ID” detailed explanation

The “Basis for specific ID” field is intended to make explicit the circumstances that led to the identification and the designation of a recording at a given level of certainty. Generally this will be whether the bird was seen, if so how well, and if a potentially difficult identification what characters were seen that led to the identification. It will also include data on whether the individual recorded was definitely seen making the sounds recorded, and if there is a realistic possibility of confusion as to which of multiple sounds in a recording is meant, a description of the sound should be provided. This is generally information recorded in the field as narration immediately post-recording, or in field notebooks. If the individual recorded was photographed, this is also indicated here, with further details on the photograph(s) presented elsewhere. Ideally, each recording should be associated with full data on how the identification was achieved, but we recognize that in field conditions this is not always practicable, and for recordings made in the past such data often have not been taken.


We strongly encourage, wherever possible, the photographic documentation of individual birds sound-recorded. This provides an excellent means of post-encounter and independent verification. Documentation should be provided as to whether the bird photographed was definitely the individual sound-recorded (“Photo(s) known to be of individual recorded?” field) . Where it is not possible to state definitively that this is the case, it may be that, for example, the bird photographed was the only bird known to be in the vicinity when the sound was recorded; that the bird photographed was present in the area around the time the sound was recorded but not at exactly the same time; that the bird photographed was a member of a mixed flock or of a flock of conspecifics and it was not possible to determine if the bird photographed was the individual or one of those recorded. Photos may be linked (in “Photo file name(s)” field) to specific recordings in any of these (and possibly other) circumstances, with the details made explicit. Photos not likely to have been of an individual or flock member recorded may appear on the site but not be linked with specific recordings. Photos of poor quality, even if diagnostic, that voucher a particular recording, are mentioned on the site [“photo numbers (if not uploaded)”] , and their numbers are listed, in case they should be important in resolving an identification or other issue, in which case they can be requested. The “Comments on photos” field contains any relevant information such as whether significant editing changes were made in the photo, or other miscellaneous information. Photos not likely to have been the bird recorded are NOT uploaded here, but can be contributed as unlinked photos. Photo filename protocol (whether linked to individual recordings or not) differs slightly from that of the recordings: e.g. Genus+species_Foldername_2-letter country code_place_photo number/ID.jpg


  • Pernis+celebensis_Philippines24Nov09-PCR_PH_PICOP.Bislig_5139.jpg, which links to recording
  • Pernis+celebensis_Philippines24Nov09-PCR_PH_NAGRA20091124.092_3-7_1_C

While it is ideal to have photographs and recordings of the same individuals, it is of course not feasible for every recordist to possess or carry both recording and photographic equipment in the field. It is certainly more difficult to make good recordings if you are also taking photographs, and vice versa. However, the effort is usually well worthwhile because of the value of this type of documentation.


Video can provide the best evidence possible as to the identity of a vocalization or other bird sound. This is certainly the case when the bird producing a sound is actually visible doing so, and its specific identity is clear in the video. The sound quality of commonly used video equipment will typically be inferior to a good recording setup, but the two forms of documentation can be used in conjunction to provide optimal baseline knowledge.